Welcome to MilkyWay@home

Posts by Frankm

1) Message boards : MilkyWay@home Science : 2012 (Message 44131)
Posted 23 Nov 2010 by Frankm
Post:
It is my hope that the these definitions will help to standardize the terminology so we can clearly discuss the rare precessional alignment that culminates in era-2012.


boooooooring

The milkyway http://en.wikipedia.org/wiki/Milkyway has over 100 billion stars. Now think, and tell me how often one of them will "align" with the "galactic equator". Statisticially, it will happen very often, and nobody has ever seen any special effects of this.

The universe is not on a 2D disk, similar to earth which turned out not be be a disk either. Crossing the "galactic equator" is nothing special. period. If you don't belief me, get youself a simple gravity simulator, and find out yourself.

2) Message boards : News : corrupted disk (Message 44129)
Posted 23 Nov 2010 by Frankm
Post:
One of our disks was corrupted.

Dont't worry. If you are lucky, the bulge and the halo are still in shape ;-)
3) Message boards : News : Milkyway Screensaver Testing (Message 42889)
Posted 16 Oct 2010 by Frankm
Post:
Just a hint on the controls:


MOVEMENT
< / > : accelerate backwards /forwards


seems to apply to us-english keyboards only. I have a german keyboard,
and i need to use to "," and "." keys for acceleration.

And i am still seeking for the equivalent of "+" and "-" ....
4) Message boards : Number crunching : GPU Requirements [OLD] (Message 41870)
Posted 1 Sep 2010 by Frankm
Post:
dcushing wrote:

Both my ATI Radian 5830's work.
Just depends on what type of Motherboard one has.


Maybe we have a misunderstanding here ...
The "Mobility HD" models are different from the "normal" Radeon HD cards. They are build into laptops, as a fixed part.
A major difference is, that most of these "Mobility HD" laptop graphics chips do not support double precision. This has nothing to do with Motherboards and overclocking..
5) Message boards : Number crunching : GPU Requirements [OLD] (Message 41851)
Posted 31 Aug 2010 by Frankm
Post:
Bad news for Laptop owners with ATI graphics:
most of the ATI Mobility HD cards do not support doubles. This is even true for the new Mobility HD 58xx models.

(See ATI Knowledge base)

The only exception seems to be the "Mobility Radeon HD 4800" Series.

6) Message boards : News : Screensaver Demo (Message 41338)
Posted 9 Aug 2010 by Frankm
Post:

I think that card [ATI 5850] should support doubles. Nearly all of the 5xxx series do, except randomly a couple don't.
-- Matt


I just looked up the specs on the ATI website. It seems that most of the newer cards support doubles, except for the Mobility cards.
In a knowledge base article (http://developer.amd.com/support/KnowledgeBase/Lists/KnowledgeBase/DispForm.aspx?ID=88) they state that only the Mobility Radeon HD 4800 Series supports doubles.

Mobility Radeon HD 5850:
# TDP: 30-39 Watts (GDDR5) or 31 Watts (GDDR3/DDR3)
# Engine clock speed: 500-625 MHz
# Memory bandwidth: 64 GB/sec (GDDR5) or 28.8 GB/sec (GDDR3/DDR3)
# Polygon throughput: 500-625M polygons/sec
# Processing power (single precision): 0.8-1.0 TeraFLOPS
(and no double precision...)

Radeon HD 5850:
# Maximum board power: 151 Watts; Idle board power: 27 Watts
# Engine clock speed: 725 MHz
# Memory bandwidth: 128 GB/sec
# Polygon throughput: 725M polygons/sec
# Processing power (single precision): 2.09 TeraFLOPS
# Processing power (double precision): 418 GigaFLOPS

7) Message boards : News : Screensaver Demo (Message 41328)
Posted 8 Aug 2010 by Frankm
Post:
Maybe it would help to look at the "abstraction" problem from the astrophysics point of view? You could merge stars based on their distance and mass/brightness once, and then use this abstracted dataset for the screensaver. If you are already looking at N-Body simulations, you could possibly re-use a spatial tree representation (like a barnes-hutt octtree); the end nodes of such a tree could be candidates for merging. Would it be possible to allow the user to control the amount of abstraction?

best regards,
Frank


"It seems you try to display a lot of points (stars). I guess many of them will be very close (at lest on the screen). Would it be possible to reduce the data to display by some kind of "abstraction" ? Maybe you can select only some representatives of the whole star dataset, based on distances to each other. Another idea would be to "merge" several stars together, and replace them by one star with an "averaged" position and brightness. What do you think?"
- Frankm

Absolutely! I have been kicking this idea around since the start of the project, but there are a few issues. The stars could be cut up into sections and averaged by using an inverse tree. This is similar to what is done when rendering textures at further distances. This tends to create a flickering effect during the transition that I considered undesirable for the screensaver. It could be overcome completely by waiting until stars were less than an 8th of a pixel apart to use their average. This did not seem necessary for the screensaver as it is now, but this mehthod would be critical for a larger-scale application using millions of stars and a larger range of distances.
- Shane Reilly
8) Message boards : News : Screensaver Demo (Message 41299)
Posted 6 Aug 2010 by Frankm
Post:
Another idea to optimize the sceensaver:

Which part will be changed more often, the Milky Way, or the wedge?
The wedge on the preview screenshot basicially looks like a slice moving in 3D. Maybe you could use a 2D surface to render the wedge into, and then let OpenGL project the data onto the "slice" in 3D?
If the Milky Way will not change, you might get some speed back by "preparing" the data once, instead of colouring and transforming it for every screen update.

best regards,
Frank.
9) Message boards : News : Screensaver Demo (Message 41298)
Posted 6 Aug 2010 by Frankm
Post:
The coloured version looks very nice!

One idea to speed up the screensaver:
It seems you try to display a lot of points (stars). I guess many of them will be verry close (at lest on the screen). Would it be possible to reduce the data to display by some kind of "abstraction" ? Maybe you can select only some representatives of the whole star dataset, based on distances to each other. Another idea would be to "merge" several stars together, and replace them by one star with an "averaged" position and brightness. What do you think?

About the ATI GPU version: I have a relatively fast ATI Mobile HD 5850 in my new laptop,
but it does not support double precision. Will there be a GPU app for single precision GPUs some day ??

Best regards,
Frank




©2021 Astroinformatics Group